In a conventional color image display apparatus of DLP (trademark) (Digital Light Processing) type using a single-plate type DMD (trademark) (Digital Micromirror Device) as an optical modulation device, tone is expressed by illuminating the DMD by light beams of three primary colors (e.g., of R, G and B), in a time-division manner, and varying ON/OFF time proportion of mirrors constituting pixels of the DMD, for each color.
In an image display apparatus using light sources of three primary colors (e.g., of R, G and B) as a backlight unit of the liquid crystal display panel serving as the optical modulation device, tone is expressed by turning on the light beams of the three primary colors in a time-division manner, and varying transmittance of each pixel of the liquid crystal display panel, for each color.
Generally, in these image display apparatuses, the light-emission period of the light source for each color and the light-emission peak value are constant regardless of the data value of the input image data. However, if the light source is made to emit light regardless of whether the image is dark or bright, the amount of light that is not necessary for the display may be increased, resulting in waste of energy and stray light.
As an improvement, it has been proposed to allot the light-emission period to each color depending on the magnitude of the input image data (brightness of the image) of each color, in an attempt to minimize the light emission of the light source, thereby to save energy, and to reduce stray light, and to increase the contrast of the image (e.g., Patent Document 1).